Ultra-thin proton-conducting phosphate glass was fabricated by press-forming at high temperature. The glass was evaluated for its ohmic loss reduction when installed as an electrolyte in intermediate-temperature fuel cells. The 36HO(1/2)-4NbO(5/2)-2BaO-4LaO(3/2)-4GeO(2)-1BO(3/2)-49PO(5/2) glass (36H-glass) was prepared by alkali-proton substitution. Herein, 3-4 mg of 36H-glass was placed onto a 50 mm-thick stainless steel or Pd support and then sandwiched by a glassy carbon plate, whereupon a 600 kg load was applied at temperatures varying as 333-391 degrees C. Ultra-thin 36H-glass with a thickness of 16 mm was successfully obtained without degradation of proton conductivity. A fuel cell incorporating the Pd-supported ultra-thin 36H-glass was successfully operated at 300 degrees C, and the ohmic loss of the fuel cell was reduced down to 2.7 Omega cm(2) from the previous reported value of several tens of Omega.cm(2). (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.